Experts warn of mosquito risk

Friday

Jul 28, 2017 at 2:51 PMJul 28, 2017 at 5:50 PM

THE ISSUE: Mosquito-borne illnesses such as West Nile virus and EEE pose a public health risk.THE IMPACT: There have been 27 mosquito sample pools to test positive for West Nile virus this year, as of July 29.

Gerry Tuoti Wicked Local Newsbank Editor

The risk of the mosquito-borne West Nile virus is expected to peak in the coming weeks, and public health officials are urging vigilance.

“Current weather patterns are likely to be supportive of West Nile virus mosquito populations,” said Dr. Catherine Brown, deputy state epidemiologist for the Massachusetts Department of Public Health. “Right now, we think there’s likely to be a moderate amount of West Nile virus mosquito activity.”

The risk of West Nile virus, which can be transmitted to humans through the bite of an infected mosquito, typically rises through the summer, peaking in August. In many cases, the disease produces no symptoms, but it can be serious for young children and people who are 50 and older. West Nile virus can sometimes produce flu-like symptoms and, in rarer cases, serious illness.

Last year, the DPH confirmed 16 human cases of West Nile statewide.

This graphic is a desktop-friendly design.

This summer, there have been 27 mosquito pool samples to test positive for West Nile virus as of July 28. The positive samples were collected in Suffolk, Worcester, Plymouth, Norfolk, Middlesex, Hampden, Essex, Franklin, Bristol and Berkshire counties.

No human cases of West Nile virus have been confirmed this year, as of July 28.

This is a mobile-device friendly design.

Controlling the risk

Gabrielle Sakolsky, entomologist and assistant superintendent of the Cape Cod Mosquito Control Project, said the types of mosquitoes that carry West Nile virus often breed in small pools of standing water, including in birdbaths, gutters, old tires and small containers in people’s yards.

“In any summer I urge people to be vigilant,” she said. “You have to assume mosquitoes out there may be carrying West Nile virus, and you have to take precautions.”

Such precautions include dumping out any pools of standing water in yards, limiting outdoor activity at dawn and dusk and using insect repellent. Sakolsky recommends using products that list an EPA number.

Bird populations and migration patterns also heavily influence the prevalence of mosquito-borne illnesses, as they may carry West Nile virus and Eastern equine encephalitis. Mosquitoes, which feed on blood, can transmit the viruses from one animal to another.

Some types of mosquitoes feed primarily on the blood of birds, while others target mammals. While there are more than 50 species of mosquitoes in Massachusetts, only a handful feast on the blood of both birds and mammals. Those vector species pose the biggest threat to humans.

EEE is rarer

Eastern equine encephalitis is rarer, but generally more serious than West Nile virus. It causes severe swelling of the brain, which is often fatal. EEE, which is most often carried by mosquitoes that breed in swamps, is typically most prevalent in interior southeastern Massachusetts.

Many of the swampy habitats where those mosquitoes breed still haven’t recovered from last year’s drought, said Brian Farless, superintendent of the East Middlesex Mosquito Control Project.

“In woodland wetlands, those populations are down a lot,” he said.

State public health officials say they are keeping an eye on the situation.

“Several years of drought have suppressed the population of mosquitoes at the start of the EEE cycle,” Brown said. “We think this year, because of the rain, it is likely going to be a rebuilding year where we may need to start thinking again about EEE as a significant risk next year. We are monitoring the situation closely.”